1. Field of the Invention
The present invention relates to a semiconductor device used as an IC chip (hereafter also referred to as an ‘ID chip’) in which required data can be stored in a memory circuit or from which data can be read by a non-contact means such as wireless communication. In particular, the invention relates to a semiconductor device used as an ID chip formed over an insulating substrate such as glass and plastic.
2. Description of the Related Art
As a computer technology and an image recognition technology advance, data recognition by using a medium such as a barcode is widely used for recognition of merchandise data and the like. It is expected that more amount of data recognition will be required in the future. On the other hand, when reading data with a barcode, there are such disadvantages that a barcode reader has to touch the barcode for reading and a barcode cannot store much data. Therefore, data recognition without contact and increase in storage capacity of a medium are demanded.
In response to such demands, an ID chip using an IC is developed in recent years. An ID chip stores required data in a memory circuit within an IC chip and the data is read out by using a non-contact means that is generally a wireless means. It is expected that commercial distribution and the like become simpler, cost is reduced, and high security is achieved by translating such an ID chip into a practical use.
An overview of an individual identification system using an ID chip is described using FIG. 4. FIG. 4 illustrates an overview of an individual identification system for obtaining individual data of a bag without contact. An ID chip 401 storing particular individual data is attached to or embedded in a bag 404. A radio wave is transmitted from an antenna unit 402 of an interrogator (also referred to as a reader/writer) 403 to the ID chip 401. When receiving the radio wave, the ID chip 401 sends in return the individual data thereof to the antenna unit 402. The antenna unit 402 sends the individual data to the interrogator 403 to identify it. In this manner, the interrogator 403 can obtain data of the bag 404. Furthermore, this system enables physical distribution management, counting, exclusion of a counterfeit, and the like.
FIG. 2 shows an example of such an ID chip technology. A semiconductor device 200 used as an ID chip includes an antenna circuit 201, a rectifier circuit 202, a stabilizing power source circuit 203, an amplifier 208, a demodulating circuit 213, a logic circuit 209, a memory control circuit 212, a memory circuit 211, a logic circuit 207, an amplifier 206, and a modulating circuit 205. Further, the antenna circuit 201 includes an antenna coil 301 and a tuning capacitor 302 (FIG. 3A). The rectifier circuit 202 includes diodes 303 and 304 and a smoothing capacitor 305 (FIG. 3B).
An operation of such an ID chip is described now. An alternating signal received by the antenna circuit 201 is processed with a half-wave rectification by the diodes 303 and 304 and smoothed by the smoothing capacitor 305. This smoothed voltage has a number of ripples, therefore, it is stabilized by the stabilizing power source circuit 203 and the stabilized voltage is supplied to the demodulating circuit 213, the amplifier 206, the logic circuit 207, the amplifier 208, the logic circuit 209, the memory circuit 211, and the memory control circuit 212. On the other hand, a signal received by the antenna circuit 201 is input to the logic circuit 209 through the amplifier 208 as a clock signal. In addition, a signal input by an antenna is demodulated by the demodulating circuit 213, and input to the logic circuit 209 as data.
In the logic circuit 209, the input data is decoded. An interrogator sends data being encoded with a deformation mirror code, an NRZ-L code, or the like and it is decoded by the logic circuit 209. The decoded data is sent to the memory control circuit 212, thereby stored data in the memory circuit 211 is read out. It is necessary that the memory circuit 211 is a nonvolatile memory circuit which is capable of storing even when the power is OFF, and a masked ROM or the like is employed. The stored content is, for example, 16-byte data (see FIG. 12A) which includes a 4-byte family code, a 4-byte application code, and two kinds of 4-byte user codes set by a user, which indicates a line of the ID chip.
As for a transmitted/received signal, 125 kHz, 13.56 MHz, 915 MHz, 2.45 GHz or the like may be employed, to which the ISO standard or the like is applied. In addition, modulation and demodulation systems in transmission/reception are standardized. Patent Document 1 is an example of such an ID chip.
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-250393